Spray foams have found widespread utility in the fields of insulation and structural reinforcement. For example, spray foams are commonly used to insulate or impart structural strength to items such as automobiles, hot tubs, refrigerators, boats, and building structures. In addition, spray foams are used in applications such as cushioning for furniture and bedding, padding for underlying carpets, acoustic materials, textile laminates, and energy absorbing materials. Currently, spray foams, especially those used as insulators or sealants for home walls, are polyurethane spray foams.
Polyurethane spray foams and their methods of manufacture are well known. Typically, polyurethane spray foams are formed from two separate components, commonly referred to as an “A” side and a “B” side, that react when they come into contact with each other. The first component, or the “A” side, contains an isocyanate such as a di- or poly-isocyanate that has a high percent of NCO (nitrogen, carbon and oxygen) functional groups on the molecule. The second component, or “B” side, contains polyols that include two or more active hydrogens, silicone-based surfactants, blowing agents, catalysts, and/or other auxiliary agents. The active hydrogen-containing compounds are generally polyols, primary and secondary polyamines, and/or water. Preferably, mixtures of diols and triols are used to achieve the desired foaming properties. The overall polyol hydroxyl number is designed to achieve a 1:1 ratio of first component to second component (A:B).
The two components are typically delivered through separate lines into a spray gun such as an impingement-type spray gun. The first and second components are pumped through small orifices at high pressure to form separate streams of the individual components. The streams of the first and second components intersect and mix with each other within the gun and begin to react. The heat of the reaction causes the temperature of the reactants in the first and second components to increase. This rise in temperature causes the blowing agent located in the second component (the “B” side) to vaporize and form a foam mixture. As the mixture leaves the gun, the mixture contacts a surface, sticks to it, and continues to react until the isocyanate groups have completely reacted. The resulting resistance to heat transfer, or R-value, may be from 4 to 8 per inch.
There are several problems associated with conventional polyurethane spray foams. For example, although sealing a building with such polyurethane spray foams reduces drafts and keeps conditioned air inside and external air outside of a building, there is a reduction in the ability of moisture to penetrate the building. As a result, the levels of moisture and air pollutants rise in these tightly sealed buildings that no longer permit moisture penetration into the building.
Another problem associated with conventional polyurethane spray foams is that the first component (the “A” side) contains high levels of methylene-diphenyl-di-isocyanate (MDI) monomers. When the foam reactants are sprayed, the MDI monomers form droplets that may be inhaled by workers installing the foam if stringent safety precautions are not followed. Even a brief exposure to isocyanate monomers may cause difficulty in breathing, skin irritation, blistering and/or irritation to the nose, throat, and lungs. Extended exposure of these monomers can lead to a sensitization of the airways, which may result in an asthmatic-like reaction and possibly death.
An additional problem with such conventional polyurethane spray foams is that residual polymeric methylene-diphenyl-di-isocyanate (PMDI) that is not used is considered to be a hazardous waste. PMDI typically has an NCO of about 20%. In addition, PMDI can remain in a liquid state in the environment for years. Therefore, specific procedures must be followed to ensure that the PMDI waste product is properly and safely disposed of in a licensed land fill. Such precautions are both costly and time consuming.
Yet another problem with such conventional polyurethane spray foams is that the reaction of the isocyanate in the “A” side with the polyol in the “B” side is a “two-part” proportioning reaction, which requires complex equipment during the formation and application of the foam. Such foams are also problematic in that it often causes the equipment to clog, resulting in time consuming clean up. In particular, the impingement-type spray guns typically used work reasonably well with a 1:1 ratio of liquids that are about the same viscosity. However, higher ratio mixtures tend to cause plugging when the larger stream overwhelms the smaller stream, allowing the reaction of the components of the “A” and “B” side to occur within the orifice. Once this happens, the gun must be disassembled and cleaned, which involves special chemicals. In addition, disassembling the gun can cost the insulation contractor a great deal of down time because it may take hours to resolve a plugging problem.
Latex foam pillows and similar items have been produced using what is known in the art as the Talalay process. In particular, the Talalay process is a batch process in which slightly foamed latex is poured into a mold to partially fill it. In this process, volatile or gas-generating substances are compounded with the latex to generate foam. The additive may be either hydrogen peroxide or a low boiling solvent. The unfrothed latex is then put into a mold. The mold is closed, and the latex expanded by vacuum to completely fill the mold. After foaming, the latex is cooled to below the freezing point of water to retard the drainage and collapse tendencies of the foam. Carbon dioxide gas is passed through the foam. The temperature is then raised to 115° C. to achieve vulcanization. The pH of the system may decrease from about 11 to 9 during the carbon dioxide addition. In a more modern Talalay process today, the latex is mechanically foamed, while the rest of the process remains the same. According to this newer process, foam is produced with compressed air in a mold and carbon dioxide is introduced into the mold at a different time. Compressed air alone will not coagulate the latex. Moreover, the Talalay process is a batch process wherein latex is poured into molds and is not a spray foam.
U.S. Pat. No. 7,053,131 to Ko et al. discloses absorbent articles that include super critical fluid treated foams. In particular, super critical carbon dioxide is used to generate foams that assertedly have improved physical and interfacial properties.
U.S. Pat. No. 6,414,044 to Taylor teaches foamed caulk and sealant compositions that include a latex emulsion and a liquid gaseous propellant component. The foamed compositions do not contain a gaseous coagulating component.
U.S. Pat. No. 6,071,580 to Bland et al. discloses an absorbent, extruded thermoplastic foam made with blowing agents that include carbon dioxide. The foam is allegedly capable of absorbing liquid at about 50 percent or more of its theoretical volume capacity.
U.S. Pat. No. 5,741,823 to Hsu teaches producing a smooth, hard coating on a wood substrate. The coating is made of a foamed, polymerized latex emulsion and is applied on the surface of a wood substrate.
U.S. Pat. No. 5,585,412 to Natoli et al. discloses a process for preparing flexible CFC-free polyurethane foams that uses an encapsulated blowing agent. The process provides a polyurethane foam having a desired density that avoids the use of chlorofluorocarbons or other volatile organic blowing agents. The encapsulated blowing agent assertedly supplements the primary blowing action provided by water in the manufacture of water-blown polyurethane foam and facilitates in the production of foam having the desired density.
U.S. Pat. No. 4,306,548 to Cogliano discloses lightweight foamed porous casts. To manufacture the casts, expanded non-porous polystyrene foam beads or other shapes are coated with a layer of neoprene, natural rubber, or other latex. The coated polystyrene is then encased in a porous envelope, and the envelope is applied to a broken limb. Additional coated polystyrene is added over the envelope and a gaseous coagulant is added to gel the latex, which causes the polystyrene beads to adhere to each other and produce a unified, rigid structure.
Thus, there is an existing need in the art for a spray latex foam that is not only safe for workers and environmentally friendly but one that also allows for moisture penetration.